Kinetics of monosodium aluminate hydrate crystallization from supersaturated sodium aluminate solutions

摘要

The study on the kinetics of monosodium aluminate hydrate (Na2O . Al2O3 . 2.5H2O) crystallization is significant for the production of sodium aluminate, and alumina by aqueous chemical process using concentrated alkali solution as digestion media. The effect of the temperature, the initial sodium hydroxide concentration, the initial molar ratio of caustic sodium oxide to alumina, and the content of silica on the crystallization of monosodium aluminate hydrate from supersaturated sodium aluminate solutions was investigated, and the kinetic equations were also extracted from the experimental data. The results show that the kinetic orders of the crystallization vary with temperature, from 2 at 60 ?? to 3 at 95 ??, while at 80℃, it changes from 2 at early stage to 3 at the latter stage of this reaction. X- Ray diffraction and scanning electric microscope were used to identify the solid phase crystallized from the solutions.